Polysaccharid chemistry

Starches – a biopolymer akin to white gold

Starch is one of the most important reserve substances of plant cells and is composed of amylose and amylopectin. Just like with cellulose, 3 hydroxyl groups per anhydroglucose unit (AGU) are accessible for derivatization reactions. Starch esters can be used, for example, as thickening, flocculation, adhesive, and sizing agents, and as tablet disintegrants. They are found in products in the food, paper, textile, medical and pharmaceutical industries.

One example for the synthesis of starch esters is the production of highly substituted carboxymethyl starches (CMS). By optimizing reaction conditions, CMS can be produced in one step with DS values up to 1.7. The products exhibit interesting rheological properties, like very high viscosity that can be greatly adjusted depending on the application.

Starch esters are also of interest for applications in the food, paper and textile industries and for medical and pharmaceutical products.
Starch phosphates exhibit a varying degree of viscosity, from firm gels to lightly flowing liquids. Highly substituted products with DS values up to 1.5 also stand out due to their high water absorption and distinctive polyelectrolyte properties.

The use of polysaccharide-based thermoplastic products, such as starch esters, is conceivable in many areas. In trials various starch esters with strengths of around 30 MPa, elasticity modules around 2 GPa and elongations at break of up to 30 percent could be achieved. A new process developed at Fraunhofer IAP for producing starch mixed esters enables the desired properties to be adjusted by greatly varying the substituents. Lower water absorption than conventional starch-based materials is another advantage of these innovative products.